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Wind-driven rain (WDR) absorbed by wall structures significantly influences moisture distribution, durability, thermal performance, and mold growth in buildings. However, the dynamic characteristics of WDR boundaries make precise quantification challenging, which is critical for simulating coupled heat and moisture transfer in building components. Traditional studies often assume a fixed WDR absorption rate, neglecting its dynamic variation under different rainfall conditions. This simplification introduces significant errors in simulating internal hygrothermal distributions, thereby affecting the assessment of building energy consumption and mold growth risks. To address this issue, this study investigates the impact of vapor barriers on wall hygrothermal loads and mold growth​under dynamic rainfall boundary conditions, based on a dynamic WDR absorption rate boundary model. Specifically, 1) Integrating a dynamic WDR absorption model into the coupled heat and moisture transfer simulation to calculate instantaneous WDR flux. 2) Simulating the effects of vapor barriers on building hygrothermal performance and mold growth for typical wall assemblies in Shanghai. 3) Evaluating the influence of vapor barriers on internal hygrothermal distributions and mold growth risk based on simulation results. The results demonstrate that, 1) The most significant difference in moisture content (nearly 10 kg/m3) between walls with and without vapor barriers occurs during autumn, leading to a 17% increase in thermal conductivity for unprotected assemblies. 2) Variations among different types of vapor barriers are negligible (< 2% relative deviation), suggesting that high-performance barriers are unnecessary in practical applications. 3) Compared to unprotected assemblies, vapor barriers increase outdoor-side mold growth rates substantially (reaching ≥ 4 mm/day); whereas reduce indoor-side mold growth rates for slow-growing colonies (< 1 mm/day). This approach enhances building envelope design/retrofit strategies, HVAC load calculations and Integration of dynamic environmental factors into building performance assessments for optimization.

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Study on Thermal and Moisture Performance of Building Walls Under Dynamic Wind-Driven Rain Boundary

  • 会议论文

  • 发表日期：

    2025年

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  • Huibo Zhang,
  • Shuo Wang,
  • Hui Yu,
  • Xing Hu

摘要

Wind-driven rain (WDR) absorbed by wall structures significantly influences moisture distribution, durability, thermal performance, and mold growth in buildings. However, the dynamic characteristics of WDR boundaries make precise quantification challenging, which is critical for simulating coupled heat and moisture transfer in building components. Traditional studies often assume a fixed WDR absorption rate, neglecting its dynamic variation under different rainfall conditions. This simplification introduces significant errors in simulating internal hygrothermal distributions, thereby affecting the assessment of building energy consumption and mold growth risks. To address this issue, this study investigates the impact of vapor barriers on wall hygrothermal loads and mold growth​under dynamic rainfall boundary conditions, based on a dynamic WDR absorption rate boundary model. Specifically, 1) Integrating a dynamic WDR absorption model into the coupled heat and moisture transfer simulation to calculate instantaneous WDR flux. 2) Simulating the effects of vapor barriers on building hygrothermal performance and mold growth for typical wall assemblies in Shanghai. 3) Evaluating the influence of vapor barriers on internal hygrothermal distributions and mold growth risk based on simulation results. The results demonstrate that, 1) The most significant difference in moisture content (nearly 10 kg/m3) between walls with and without vapor barriers occurs during autumn, leading to a 17% increase in thermal conductivity for unprotected assemblies. 2) Variations among different types of vapor barriers are negligible (< 2% relative deviation), suggesting that high-performance barriers are unnecessary in practical applications. 3) Compared to unprotected assemblies, vapor barriers increase outdoor-side mold growth rates substantially (reaching ≥ 4 mm/day); whereas reduce indoor-side mold growth rates for slow-growing colonies (< 1 mm/day). This approach enhances building envelope design/retrofit strategies, HVAC load calculations and Integration of dynamic environmental factors into building performance assessments for optimization.